I9I4-] SOUTHEASTERN NORTH AMERICA. 213 



The Helictereas are represented by a doubtful species of Hehc- 

 teres Linne described from the Pliocene of Italy and by forms 

 referred to the existing genus Pterospermum Schreb. or to the 

 extinct genus Pterospermites Heer. Over 30 species have been de- 

 scribed. There are nine or ten in the Upper Cretaceous all of which 

 are Xorth American, and their combined range extends from New 

 York to western Alabama, throughout the Rocky Mountain and 

 Great Plains province and in the Atane beds of Greenland. There 

 are about a dozen Eocene species all Xorth American except a single 

 species in the Paleocene of France. The American forms extend 

 northward to West Greenland and Alaska. There are two or three 

 species in the European Oligocene and ten Miocene* species through- 

 out Europe and in western Xorth America (Yellowstone Park, Cali- 

 fornia, mouth of the Mackenzie River). A single Pliocene species 

 is recorded from France. It seems probable that this type originated 

 in the western hemisphere since it is so abundantly represented in 

 that region during the Upper Cretaceous and Eocene. The modern 

 species of Pterospermum are, however, confined to eastern tropical 

 Asia. 



The order Parietales includes thirty families together with over 

 four thousand existing species, the largest families being the Gut- 

 tiferae (775), Flacourtiaceae (530), Begoniaceoe (425), Violacese 

 (400) and Dipterocarpacese (330). Xone of these families are 

 present in the Wilcox flora, where the order is represented by the 

 two families, the Dilleniaceae and Ternstrcemaceae. The Parietales 

 are prevailingly syncarpous and show affinities with the Ranalian 

 plexus tli rough the Dilleniaceae which were formerly referred to that 

 order. The alliance as a whole is a complex one including several 

 divergent lines of development with, on the whole, a gradual increase 

 in floral complexity. 



The family Dilleniaceae contains 14 genera and about 275 exist- 

 ing species found on all the continents, the genus Tctracera being 

 cosmopolitan in the tropics. The genera Empedoclea, Curatclla, 

 Doliocarpus and Darilla together with 50 species are confined to 

 the American tropics : Hibbertia and Pachynema together with 75 

 species are Australian, there are five genera with about 25 species 

 confined to the Asiatic tropics; the genus Saurauia (or Saurauja), 



